According to the book "The 5 Love Languages: The Secret to Love that Lasts" by Gary Chapman, there are five love languages that people speak. Try out all of the languages on your partner and see how he/she is reacting to them. Most of the people have one primary love language.

Examples of how to talk in each language

Words of Affirmation
Spoken words must be sincere
- Give compliments e.g. "You always make me laugh.", "That dress looks incredible on you!", "I love your hair today."
- Encourage in doing what your partner likes
- Give less negative comments

Acts of Service
Things must be done with positivity and not out of obligation
- Be proactive with the daily chores
- Cook a dinner
- Help with laundry

Receiving Gifts
It isn't necessarily materialistic
- Buy the favorite ice cream after a long walk
- Buy tickets to do some activity together
- Make something with your own hands (painting, origami, love letter)

Quality Time
The partner needs to be in the center of attention
- Have a talk on a couch without any background noise (tv, smartphones, radio, etc.)
- Go for a long walk just two of you without any destination
- Play a board game together

Physical Touch
Have as much physical connection as possible
- Kissing and holding hands
- Massage
- Occasional body touch

Try out all languages until you find out the primary one.
You can find out more information in the book:
https://www.amazon.com/Love-Languages-Secret-that-Lasts/dp/080241270X